Despite the wide diversity of available solar technologies, solar energy systems are still not considered as main stream technologies in building practice. So far most photovoltaic systems are optimized only for efficiency which implies absorbing a maximum number of photons, and hence leading to a dark blue and ideally black color appearance. Most of the photovoltaic cells on the market are crystalline cells with connecting ribbons which have an unaesthetic appearance.
One of the reasons of the lack of wide spread use of solar technologies for buildings is the lack of awareness and knowledge of integration possibilities among architects and the lack of solar products designed for building integration. In parallel there is a recent trend to transform buildings from energy users to energy producers. The old wide spread concept of adding solar panels on the roof of a building has evolved and a lot of effort is being done to merge the construction technology with the science and technology of photovoltaics in what is called the Building Integrated Photovoltaics. Architectural, structural and aesthetic solutions are being constantly seeken to integrate solar photovoltaic elements into buildings, allowing the incorporation of energy generation into everyday structures such as homes, schools, offices hospitals and all kind of buildings. Photovoltaic modules can have a wide variety of functions such as noise protection, safety, electromagnetic shielding, thermal isolation etc. Photovoltaic elements can also be used to combine these functions with an aesthetic function. With such an approach solar photovoltaic modules become more and more construction elements serving as building exteriors such as façades and inclined roofs. If well applied, solar photovoltaic cells can increase a building's character and its value.
The more technologies will be available to create aesthetic effects with photovoltaic cells the more the technology will be accepted and costs will decline. Not only new building construction will profit from this trend but also the improvement and modification of existing buildings. Architects who apply Photovoltaic cells in an intelligent manner can as such contribute largely to the acceptance of this technology.
One of the technology improvements would be to dispose of a solar photovoltaic module that has an appearance that is more aesthetic than the classical blue-black appearance. In other approaches front colored glass is integrated with the photovoltaic modules, such as explained in the following publication: “Efficiency of silicon thin-film photovoltaic modules with a front colored glass; S. Pélisset et al., Proceedings CISBAT 2011, pp. 37-42.” In other approaches technology solutions have been initiated to render a specific color to a photovoltaic cell by the deposition of multilayer antireflection coatings on such photovoltaic elements, as for example described in the article: “Reduction of optical losses in colored solar cells with multilayer antireflection coatings; J. H. Selj et al., Solar Energy Materials & Solar Cells 95, pp. 2576-2582, 2011”.
EP 2051124 discloses a design comprising, to the incident light side of the photoconversion element, a passive interference filter or an addressable optical resonance cavity, allowing to produce a specific color to an observer. The design in EP 2051124 requires a complex and expensive technology and is limited to produce specific colors, excluding white and grey and does not allow to produce a mate appearance of these colors.
In all approaches of prior art it is necessary to add additional light diffusing layers to a photovoltaic cell, such as a colored glass plate or an interference filter, which makes the realization process complex and expensive and it may also reduce the photoconversion efficiency. It is the objective of the present invention to bring a new approach in this field.